1. Field of the Invention
The present invention relates to a pin plug for electrically connecting between various elements, for example, between electronic equipments, between an equipment and an electric power source or between conductor leads. More particularly, the invention relates to a pin plug adapted to be attached to an end of a conductor lead to be connected to a pin jack.
2. Related Background Art
In an example of a conventional pin plug, as shown in FIG. 1, a lower end of a hollow pin 31 is fixedly embedded into a resin insulation member 32 by a resin-injection molding process, and a metal spring sleeve 33 is fitted around an outer peripheral surface of the insulation member 32. A solder material 34 is previously inserted into the pin 31. A core wire 36 of a conductor lead 35 of coaxial cable type is inserted into the pin 31, and shield wires 37 are connected to the spring sleeve 33. Thereafter, the solder material 34 is heated and melted, with the result that the core wire 36 is electrically and mechanically secured to an inner surface of the pin 31. Then, a resin cap 38 is attached so as to surround the metal spring sleeve 33 and the conductor lead 35.
However, the above-mentioned conventional example has the following disadvantages:
(1) Since a soldering operation space for treating the solder material 34 is small, it is difficult to perform the soldering operation, and the soldering operation therefore requires expert skill. Accordingly, there can be uneven strength in the connection between the pin 31 and the core wire 36, resulting in poor conductivity and frequent disconnection of the core wire from the pin. PA1 (2) Harmful gas generating from solder flux during the soldering operation can be a bad influence upon an operator's health. Although flon gas frequently has been used to clean the soldering bath and/or to remove the flux, flon gas has recently been inhibited from use because it destroys the ozone layer. PA1 (3) A process for integrally forming the protruded portion on the pin 31 is troublesome, and it is difficult to automatically perform the engaging operation (for engaging the core wire with the protruded portion) and the caulking or crimping operation, and such operations become unstable frequently, thereby causing uneven or poor mechanical connection and electrical conductivity between the pin and the core wire. PA1 (4) In a further conventional example, core wire 36 is inserted into a hollow portion of pin 31 and the pin 31 itself is deformed so as to contact with the core wire 36 by caulking the pin 31. However, in this case, since an amount of deformation of the pin 31 is limited from the viewpoint of the appearance of the pin, the contact between the pin and the core wire is inadequate, and thus good mechanical connection and electrical conductivity (between the pin and the core wire) cannot be achieved. PA1 (1) Since the crimping operation can be performed by using a punch and the like, the crimping operation can be easily performed uniformly and effectively by any person without expert skill even within a narrow space, in contrast to a soldering operation, the strength of the mechanical connection between the pin and the core wire is stabilized, the electrical conductivity between the pin and the core wire is improved, and disconnection of the core wire from the pin can be prevented, thereby obtaining uniform and high quality articles. PA1 (2) Since there is neither generation of harmful gas from the flux used in a soldering operation nor the need to use flon gas (because the soldering operation can be omitted), the operator's health is not subjected to such dangerous conditions and danger to the ozone layer can be prevented. PA1 (3) Since there is no need to form a protruded portion on the pin to connect the core wire to the pin, the manufacturing process of the pin is simplified. Further, since there is no need to perform the troublesome connection between the protruded portion and the core wire, reliability of the article and operability thereof are improved. PA1 (4) Since the crimping operation is performed after the core wire is inserted into the insert which is previously inserted within the pin, a gap between an outer diameter of the core wire and an inner diameter of the insert becomes very small, with the result that, when the pin is deformed by the crimping operation, the pin is adequately urged against the core wire, thereby not only protecting the appearance of the pin itself but also providing good mechanical connection and electrical conductivity between the pin and the core wire. PA1 (5) Since the large diameter portion of the insert is firmly press-fitted against the inner surface of the pin, during the crimping operation, the insert can be displaced neither in an axial direction nor in a direction perpendicular thereto, with the result that a stable crimping condition can be achieved, thereby providing more stable mechanical connection and electrical conductivity between the pin and the core wire. PA1 (6) Since the inner diameter of the insert corresponds to the outer diameter of the core wire to provide no gap therebetween, there is no place where the core wire escapes during the crimping operation. Thus, the deformed portion of the insert is effectively penetrated into the core wire, thereby providing more stable mechanical connection and electrical conductivity between the core wire and the pin. PA1 (7) With this arrangement, since the two outer diameter portions of the insert having different outer diameters are steppingly press-fitted against the inner surface of the pin, even if there is variation in dimension between an inner diameter of each of the pins and an outer diameter of each of the insert, such variation is accommodated by the two outer diameter portions of the insert, thereby always achieving a good press-fit condition of the insert and providing a more stable construction.
In another conventional example, core wire 36 is engaged with a protruded portion integrally formed with a lower end of pin 31, and the protruded portion is deformed by caulking or crimping to electrically connect the core wire 36 to the pin 31. However, this technique has the following disadvantage: